Human Nature and the Neurobiology of Conflict

Areas of inquiry once reserved for historians and social scientists are now studied by neuroscientists, and among the most fascinating is cultural conflict.

Science alone won't provide the answers, but it can offer new insights into how social behavior reflects -- and perhaps even shapes -- basic human biology.

An upcoming issue of the Philosophical Transactions of the Royal Society B features a collection of new studies on the biology of conflict. On the following pages, Wired looks at the findings.

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Left versus Right, in the Brain

Research has already shown that, compared to liberals, conservatives display heightened responses to threatening images. Michael Dodd of the University of Nebraska wanted to explore this in finer detail: He showed 46 left- or right-leaning Nebraskans a series of images alternately disgusting (spiders on faces, open wounds) and appealing (smiling children, cute rabbits.) Dodd's team found that conservatives reacted most strongly to negative images, and liberals most strongly to positive photographs.

Then he showed them pictures of well-known politicians. The same patterns held: Conservatives displayed more distaste than liberals for politicians they disliked, while liberals felt more positive than conservatives about politicians they liked. Given these and other findings, wrote Dodd's team, "those on the political right and those on the political left may simply experience the world differently."

That sounds pessimistic, but it doesn't have to be. It can be a healthy reminder that people with whom we disagree aren't stupid or irrational; they just have different perspectives.

Image: Each graph depicts the arousal response of conservatives (triangle dots) and liberals (square dots) to images that are disgusting or appealing (left set) and pictures of opposing politicians (right set). (Dodd et al./Philosophical Transactions of the Royal Society B)

Economics, Rationality and Values

Economists have traditionally viewed markets as places where people are motivated by rational self-interest. Even when their decisions seem irrational -- like thinking the value of tulips will keep going up -- their underlying interest is straightforwardly selfish.

In practice, however, market participants are also "altruistic and fair, envious and status-seeking," write Duke University researchers Scott Huettel and Rachel Kranton. People are complicated; they're often motivated by factors, especially social factors, other than money and self-interest. Huettel and Kranton propose a field of research they call "identity neuroeconomics": Applying neuroscientific tools to better understand how social values affect thought processes and ultimately economic decisions.

An early focus of the research could involve transactions between people who have strong or weak social ties, or between people allowed to know the other's identity or kept anonymous -- an especially relevant set of conditions in a global economy that allows both intimate long-distance cooperation and complete facelessness.

The Male Warrior Hypothesis

Tribalism is a classic human behavior: We're nice to people in our groups, and suspicious if not downright hostile to strangers. The tendency is so ingrained and historically ubiquitous as to seem natural. But exactly why this state of mind prevailed during human evolution is unknown.

According to evolutionary psychologist Melissa McDonald of Michigan State University, it's an indirect consequence of reproductive biology. Female reproduction is limited by physiology, while male reproduction is -- generally speaking -- limited by access to partners. As a result, males compete fiercely within their groups for mates. Alliance-building shifts the focus of competition to groups of other males, and their females are the reward. Over evolutionary time, what McDonald calls "the warrior male" emerges.

"If men's psychology is designed in ways that facilitate success in intergroup conflicts, evidence for the workings of the mechanisms should be apparent in the thoughts, emotions, motivations and behaviours relevant to intergroup conflict among men in modern societies," she writes, and indeed it is. Men tend to be more xenophobic, more reliant on stereotype, and endure greater sacrifice to ensure the punishment of others -- so long as those others are men.

The Mystery of Monogamous Marriage

Monogamous marriage isn't just strange in evolutionary terms, but in relation to human history: Approximately 85 percent of societies known from the anthropological record allowed men to marry multiple wives, and that tendency actually became more pronounced with the advent of agriculture and social complexity.

Why, then, has monogamous marriage prevailed? Psychologist Joseph Henrich of the University of British Columbia thinks it's socially beneficial: If relatively few men will get to marry and reproduce, men will compete fiercely for the chance, and that translates into rape and murder, assault and deception. Monogamous marriage reduces the competition, making communities more stable and -- in terms of cultural evolution -- better able to compete against unstable, non-monogamous communities.

Citation: "The puzzle of monogamous marriage." By Joseph Henrich, Robert Boyd and Peter J. Richerson. Philosophical Transactions of the Royal Society B, Vol. 367 No. 1589, March 5, 2012.

(Im)patience and Culture

Just as some people are better than others at delaying gratification in exchange for greater reward, so are some cultures. People from the west generally prefer immediate reward; people from the east are generally more patient.

To learn more about how these tendencies manifest in our minds, researchers led by psychologist Bokyung Kim of Stanford University scanned the brains of American and South Korean students as they decided whether to accept an immediate cash payment or a slightly larger sum in two weeks. They observed large activity differences in brain regions involved with reward (pictured above), but surprisingly little difference in regions involved with self-control. Americans weren't necessarily impulsive or undisciplined. Instead, the promised reward literally felt more valuable to them.

Image: Activity in reward-linked brain regions of American and Korean test subjects presented with a choice between immediate and delayed payments. (Philosophical Transactions of the Royal Society B)

Group Intelligence

When cognitive scientist P. Read Montague of Virginia Tech's Carilion Research Institute administered intelligence tests to people individually and in groups of five, they found that IQ actually dropped in the social setting.

"Individuals express diminished cognitive capacity in small groups," wrote Montague's team, and they're not sure why, though they suspect that social pressure plays a role. Groups have hierarchies and pecking orders; stress and intimidation could translate into compromised cognition.

Conflict and Empathy

When groups are in conflict with each other, people are less empathic and compassionate toward their enemies. It's a self-evident truth, reinforced by controlled laboratory studies of conflict. But when cognitive scientist Emile Bruneau of the University of Massachusetts looked at the brains of people involved in the Arab-Israeli conflict, he found something very unusual.

Bruneau read stories of Arab and Israeli suffering to members of each group. As expected, each group expressed compassion for its own members, and little empathy toward its rivals. In areas of their brains linked to empathy, however, there was no difference: For Arab participants, Israeli tragedy elicited the same empathic response in the brain as an Arab tragedy, and vice versa. Brain and behavior seemed disconnected.

"The absence of any region whose neural response mirrors the pattern of behavioural judgements is puzzling," wrote Bruneau's team. It may simply reflect a limitation of the tests -- or perhaps our minds work very differently than we think.

Violence, Society and Evolution

Why do people risk their own safety to avenge grievances against total strangers? As a rule, violence is more common in groups with stronger collective identities, where an individual's fate is bound to its community's.

Psychologist Michele Gelfand of the University of Maryland wonders if the tendency to risk oneself for the greater good could, over time, become embedded in biology as well as culture. In certain conditions, it could be a beneficial adaptation; to the extent it represents heritable biological traits, those should become more common.

It's a prickly line of thinking, to be sure, and utterly unproven. It might also be impossible to test, as the genetic underpinnings of behavior have proved extremely difficult to identify.

The Neurobiology of Integrity

The fundamental origin of our dearest beliefs is a centuries-old philosophical question: Do they reflect, as Kant claimed, deep and pure principles? Or, per Jeremy Bentham, are they elegantly rationalized cost-benefit analyses?

Neuroscientist Greg Berns of Emory University put this question to the test in a brain scanner. He found that when people refused to accept cash for stating beliefs opposite to their own, it wasn't simply because the cash wasn't enough. Reward-calculating parts of their brains weren't even part of the equation; instead, activity occurred in rule-processing, right-or-wrong systems. Principle was truly principled.

Across the Aisle

In the month leading up to the 2008 election, researchers led by the University of California, Los Angeles psychologist Emily Falk performed brain scans on self-identified Republicans and Democrats as they considered statements from each Presidential candidate.

As the election neared, brain areas linked to emotion and social cognition were intensely active. Areas linked to logic and rational thought, however, were relatively inactive.

The lesson: When people are certain of their rightness, it's worth taking a mental step back and considering whether our certainty is the product of many factors, of which rational deliberation is only one -- and not necessarily the strongest. "Within our brains, we may yet still have untapped potential for social connection across the aisle," wrote Falk's team.